Research will continue on the problem of distinguishing between cognitive and perceptual factors in reports of size and distance. For this purpose, a technique which seems to be immune to cognitive factors in the measurement of perceived distance will be used to evaluate the effect of cognitive factors upon verbal reports of distance. Also, research will be conducted to determine whether the specific distance tendency can be considered to be caused by or to cause the correlated tendency for the resting state of convergence to be at a near distance. Finally, the role of apparent distance in motion after effects will be investigated and used to evaluate the explanation of such aftereffects in terms of the differential adaptation of feature detectors.